hi there,
im new to arduino but loving it.
im running out of pins on my arduino,
digital and analog, how do i add more? is there a product?
Charl.
You can google these:
Shift Registers
Multiplexing
Charlieplexing
System redesign? :
cool, thanks.
I need to switch a 12v fan on when a certain condition is met, do i need a relay for this as arduino only offers 5v?
Is this only for switching 220v?
Bite the bullet:
Or my favorite:
Running out of pins would be a vague memory 
Lefty
The cheap (<1 dollar) and easy way is to use a 74HC595 shift register for more digital I/O's and a 4051 analog multiplexer for more analog in's. Try searching this website for examples...
I need to switch a 12v fan on when a certain condition is met, do i need a relay for this as arduino only offers 5v?
I'm no wiz but it sounds like a TRANSISTOR could solve that problem?
EDIT: Forget what I said about the transistor. I doesn't handle voltage much higher than 5V. I think you do need a relay. Like I said I'm no wiz :-X
70 IO Pins? O_o
Wow, You could pretty much make an LCD controller with that without any extra hardware! XD